Numerous wood products in use today, such as fence posts, railroad ties, and dimensional lumber are dependent upon diminishing forest reserves as a source of material. For numerous applications, wood products are especially vulnerable to rot and decay from excessive exposure to moisture, insects, dry-rot and other conditions that cause deterioration to the product. Wood products must be coated with preservatives of various types when they are to be exposed to the environment. For example, railroad ties and fence posts have long been treated with creosote under pressure to protect the wood from moisture and boring insects. Special treatments and application of protective coatings of paints and oil add appreciably to the cost of wood materials, and none are known to offer indefinite protection. The use of petroleum based preservatives tend to add some pollution to the environment.
Products have been made utilizing waste materials such as old automobile tires, waste plastics, and resinous thermoplastic materials. Products made from these materials are made utilizing heat and pressure to extrude products. Examples of such processes are defined in U.S. Pat. Nos. 4,028,288 and 4,191,522. The heat and extrusion process usually involves temperature in excess of 450 degrees Fahrenheit. This presents problems when the waste products include polyvinyl Chloride (PVC). PVC materials are volatile, explode, and produce gases when exposed to heat at elevated temperatures. Even small amounts of PVC, as small as one percent, can be disastrous. Since it is difficult to separate PVC materials from waste recycled materials, extruding products from recycled material is not desirable.